1. Technical Field
The present invention relates to reproduction of a multi-session disc.
2. Background Art
A compact disc (CD) was formerly the media in which the user could not write data. At the present, write-enable media are developed, such as compact disc recordable (CD-R) or compact disc rewritable (CD-RW). Such media can be manufactured and reproduced by disc recording and reproducing apparatus for the media.
A disc recording and reproducing apparatus can manufacture CD-R and CD-RW not only as ordinary single-session CD but also as multi-session CD. A “session” is a recording unit formed on a disc. FIG. 5 shows a data layout example of a disc recorded in a single session. The single-session disc is composed of one lead-in LI, a program area PA, and a lead-out LO. As index information, table-of-contents information (hereinafter referred to as TOC information) is recorded in lead-in LI. A conventional CD and compact disc read-only memory (CD-ROM) are single-session CDs. A multi-session CD is a CD composed of plural sessions manufactured by once recording partially on a CD-R or CD-RW, and adding sessions after the recorded portions. FIG. 6 shows a data layout example of a disc recorded in multiple sessions. The multi-session disc shown in FIG. 6 includes a plurality of sessions (M pieces (k=1 to M)) composed of lead-in LI (k), program area PA (k), and lead-out LO (k). In each lead-in, contents information is recorded as TOC information. The TOC information in each lead-in area LI of multi-session CD includes, aside from the position information of the own session, start time information of program area PA of next session. This is different from the TOC information of single-session CD.
In a multi-session CD, data and audio (CD-DA) can be recorded in each session. These sessions are called data session and audio session. In a multi-session CD, data sessions and audio sessions can be mixed and recorded in a same disc.
FIG. 7 shows an example of composition of multi-session CD including an audio session in the last place. On the other hand, FIG. 8 shows an example of composition of multi-session disc including an intermediate audio session. Generally, a multi-session CD is manufactured in a procedure comprising the steps of recording one or plural tracks in program area PA of each session, recording an ISO 9660 file system, and recording track information of corresponding session and start timer information of program area of next session in lead-in area LI of the same session. In this process, if additional writing is not allowed in the disc, start time information of program area of next session is not recorded in lead-in area LI.
When recording computer-readable data on a disc, generally, an ISO 9660 file system is used. What is recorded by using this system is a data session. The ISO 9660 file system manages the data in the file unit, and builds up a hierarchical structure by using a directory. In a multi-session CD composed of plural data sessions, the ISO 9660 file system information described in the data session at the inner peripheral side can be added to the ISO 9660 file system information of next data session. Accordingly, by analyzing the ISO 9660 file system of the final session of the multi-session CD, it is allowed to access all files in the multi-session CD. For example, in the multi-session CD shown in FIG. 6, if all of session 1 to session M are data sessions, by analyzing the ISO 9660 file system of the final session M, it is possible to access all files in the multi-session CD.
However, as shown in FIG. 7 or FIG. 8, when audio sessions are recorded on a same disc, the ISO 9660 file system information described in the data sessions at the inner peripheral side thereof cannot be added to the ISO 9660 file system information of next audio session. Therefore, if the ISO 9660 file system of the final session of the multi-session CD is analyzed, all files in the multi-session CD cannot be accessed. In the examples in FIG. 7 and FIG. 8, it is impossible to refer to the sessions before the final session (session 5).
Next, operation of conventional disc reproducing apparatus is explained. FIG. 9 is a block diagram showing a configuration of a conventional disc reproducing apparatus 60. A reproducing unit 2 for reproducing data from a disc can be loaded with a disc 1 to be reproduced, and comprises mechanical units such as a pickup for reproducing data from the loaded disc 1. Reproducing unit 2 detects start position information of program area from the lead-in area at the innermost peripheral side, and transfers the optical pickup to this position, and detects a signal from the program area. A signal processing unit 5 demodulates (decodes) the data from reproducing unit 2 from data format of recording format. A data storage unit 10 temporarily stores the demodulated reproduction data. A control unit 4 controls the general operation of the disc reproducing apparatus. For this purpose, control unit 4 incorporates a program for controlling a general operation of the disc reproducing apparatus. Control unit 4 controls to store the reproduction data outputted from signal processing unit 5 temporarily in data storage unit 10.
Generally, when reproducing a multi-session CD by conventional disc reproducing apparatus 60, first of all, disc reproducing apparatus 60 sequentially inspects the lead-in area of the multi-session CD, recognizes the final session, and starts operation for reproduction. More specifically, the procedure is as follows. That is, when a multi-session CD (FIG. 6) is inserted into disc reproducing apparatus 60, control unit 4 positions an optical pickup (not shown) in lead-in area LI (1) of first session of the disc innermost peripheral portion, and recognizes the start address of program area PA (2) of second session. In succession, the pickup is moved to program area PA (2) of second session, and it is inspected if data is recorded or not. At this time, when data is read out from program area PA (2), the pickup is moved again in the direction of inner periphery of CD to read the start address of program area PA (3) of next third session from the position of lead-in LI (2) of second session. Further, the pickup is moved to program area PA (3), and it is inspected again to see if data is recorded or not. In this manner, disc reproducing apparatus 60 inspects the state of each session while repeating up to the final session of session M.
In this period of repeated inspection, when it is known that next session start time information is not recorded in lead-in area LI (k) of session k, or that data is not recorded in program area PA (k+1) of session k+1, at this moment, disc reproducing apparatus 60 judges that session k is the final session, and moves the pickup to a region or area before session k having recorded data, and starts analysis of ISO 9660 file system.
In succession, the procedure of reproducing music data on disc is as follows. Control unit 4 demodulates data signal from data storage unit 10 into analog music signal in an audio demodulation amplifier 11, and outputted as a sufficiently large electrical signal from a speaker 12. For controlling general operation of the disc reproducing apparatus, control unit 4 once reads out the TOC information in the lead-in area at the inner peripheral side of disc 1 through a signal processing unit 5 and a sub-code detecting unit 6, and stores in a TOC information storage unit 7. By first reading the TOC information and displaying the track information on disc 1 in a display unit, disc reproducing apparatus 60 urges the user to select a desired tune to be performed. When the user selects tune, control unit 4 fetches start address information of the track to be reproduced from within the program area, and moves the optical pickup to this position, and reads out the music data signal. Control unit 4 operates in this way according to the specified program.
Therefore, when a disc is loaded into disc reproducing apparatus 60, disc reproducing apparatus 60 moves the pickup to lead-in area LI in order to read in the TOC information. For this operation, it is required that the present pickup position should be recognized. The pickup position can be recognized, for example, by making use of the detection voltage of the potentiometer changing depending on the pickup position. More specifically, by driving a stepping motor, linear motor or the like depending on the detection voltage of the potentiometer, the optical pickup can be moved at high precision. However, the potentiometer and linear motor are expensive and elevate the cost. Instead of the position sensor such as potentiometer, therefore, it is known to use an inexpensive push switch for detecting position which is turned on only when the optical pickup is positioned nearly on the innermost periphery. FIG. 10A to FIG. 10C show a configuration of an inexpensive mechanism employing this technique.
Referring to FIG. 11, the following is the explanation of reproducing a multi-session CD (FIG. 6) recording only data session loaded in disc reproducing apparatus 60 (FIG. 9). FIG. 11 is a flowchart of reproduction of multi-session CD data by disc reproducing apparatus 60. In the mechanism of disc reproducing apparatus 60 (FIG. 9), when a multi-session CD is loaded, control unit 4 (FIG. 9) cannot always recognize the position of the optical pickup. Accordingly, control unit 4 first moves the traverse incorporating the optical pickup in the inner peripheral direction in order to position the optical pickup nearly on the innermost periphery of disc 1 (step 21). When the optical pickup comes nearly to the innermost periphery of the disc, the traverse is moved in the outer peripheral direction for a specific time, and is stopped (step 22). When the optical pickup accesses the first lead-in LI (1), by reading the sub-code, the TOC information is read in (step 23), and this session is judged to be data session or not (step 26). If it is not data session (NO at step 26), it is judged to be an audio session, and CD-DA signal is processed (step 35). In the case of data session (YES at step 26), on the other hand, it is judged to be a multi-session or not depending on whether program area start position information of next session is present or not in the TOC information (step 27).
If there is no program area start position information of next session in the TOC information, and it is judged not to be a multi-session disc (NO at step 27), it is included to be a single-session disc, and the process corresponding to the single-session is executed (step 34). On the other hand, if there is program area start position information of next session in the TOC information, it is judged to be a multi-session disc (YES at step 27), and accessed the next session (step 28). The TOC information of sub-code of next session is read in (step 29), and it is judged if this session is the final session or not (step 32). It is judged at this step 32 by detecting that program area start address of next session is not recorded in TOC information of present session, or that next session is not actually recorded if program area start address of next session is recorded.
As a result of detection, if judged not to be final session (NO at step 32), it means that a next session is present, and the process returns to step 28, and the process at step 28, step 29, and step 32 is repeated. If judged to be final session (YES at step 32), the present session (for example, session M in FIG. 6) is regarded as final session, and the multi-session process for accessing the specified multiple sessions is executed (step 33).
In disc reproducing apparatus 60 (FIG. 9), when reproducing a multi-session disc (FIG. 7), disc reproducing apparatus 60 accesses up to session 5 in an attempt to acquire the address of next session. However, address information of next session does not exist, and hence it is attempted to analyze the file system, assuming session 5 as final session. Session 5 is an audio session, and audio data (CD-DA) is recorded, and there is no file system information about data session of session 1 to session 4. As a result, an inaccessible phenomenon occurs in the data for reproduction of session 1 to session 4.
Also in disc reproducing apparatus 60 (FIG. 9), when reproducing a multi-session disc (FIG. 8), disc reproducing apparatus 60 accesses up to session 4 in an attempt to acquire the address of next session. However, address information of next session does not exist, and hence it is attempted to analyze the file system, assuming session 4 as final session. Session 4 is an audio session, and audio data (CD-DA) is recorded, and there is no file system information about data session of session 1 to session 3. As a result, an inaccessible phenomenon occurs in the data for reproduction of session 1 to session 3.
Therefore, in the conventional disc reproducing apparatus 60, if the ISO 9660 file system of final session is analyzed, information of data session of inner side than audio session cannot be acquired, and it was impossible to access the data section of the inner side.
The conventional disc reproducing apparatus 60 (FIG. 9) involved one more problem. That is, in disc reproducing apparatus 60, when reproducing the disc recorded in multiple sessions, if the data quantity stored in the first session is small, the data not intended to be reproduced was sometimes reproduced by mistake. The reason is that, owing to the small capacity of data stored in the first session, the access for reading the TOC information of the first session has surpassed the recorded portion of the first session to get into lead-in of next session 2. As a result, the TOC information of other session is read and stored. A radical reason of such malfunction is that most commercial music audio CDs are recorded in single session, not in multiple sessions, and hence disc reproducing apparatus 60 is designed to reproduce single-session discs only.
It is more specifically described. FIG. 12 is a diagram showing data composition of multi-session disc including audio sessions. FIG. 13 is a diagram showing a detailed data composition of left end portion of FIG. 12 (the portion of session 1 and session 2). As shown in FIG. 13, in session 1 of this disc, a very short audio session of 20 seconds is recorded. When this disc is reproduced by the conventional disc reproducing apparatus 60 (FIG. 9), at step 22 (FIG. 11), surpassing session 1 (audio session), it gets into lead-in L1 (2) of session 2. When the TOC information is read at step 23 (FIG. 11), only the portion after session 2 is recognized, and the CD-DA process (step 35) of session 1 to be executed may not be executed.